Troubleshooting the issue of not being able to remotely connect to a server using SSH and steps to diagnose the issue.
There could be various reasons for the failure to establish an SSH remote connection to the server. Here are some common troubleshooting steps for identifying the causes of the issue.
- Check the local network connection first and try pinging the server to see if it can be reached.
- The SSH service is not running: Check if the SSH service is started on the server, you can use the systemctl command to check the service status.
- Firewall configuration: Verify the server’s firewall settings to ensure that the SSH port (default is 22) is open, and configure it using the iptables or firewalld commands.
- SSH configuration file: Verify the SSH configuration file on the server (usually located at /etc/ssh/sshd_config) to ensure that the settings are accurate. Pay particular attention to the following configuration options:
- Port: Ensure the correct port is being used for SSH.
- AllowRootLogin: Confirm whether the root user is allowed to login via SSH.
- PubkeyAuthentication: verifying if public key authentication is enabled.
- PasswordAuthentication: Verify if password authentication is enabled.
- Confirm that the local SSH key is configured correctly. You can use the ssh-keygen command to generate a public and private key, and then add the public key to the server’s ~/.ssh/authorized_keys file.
- User permission issue: Check if the user has SSH access rights for remote connection, you can edit the /etc/sudoers file using the visudo command to ensure the user has the necessary permissions.
- Log File: Review the SSH log files on the server (usually located at /var/log/auth.log or /var/log/secure) to search for any error messages related to failed connections.
- Restart SSH service: If none of the above steps resolve the issue, you can try restarting the SSH service on the server by using the command systemctl restart sshd.
If the issue cannot be resolved, it is recommended to consult the official documentation of the SSH service or seek advice from relevant technical support personnel.
